The present invention relates to a system of electric coupling between a connection electrically connected to a current output terminal, and an electrochemical bundle. It moreover extends to the method for producing this coupling.
An electrochemical generator comprises an electrochemical bundle comprising an alternating sequence of positive and negative electrodes framing a separator impregnated with electrolyte. Each electrode most often comprises a metal current collector supporting on at least one of its surfaces the electrochemically active material. The electrode is connected electrically to a current output which ensures electrical continuity between the electrode and the external application with which the generator is associated. This current output can be the container of the generator or a current output terminal.
There are several ways of electrically coupling an electrode to a current output terminal. One of these ways is the use of a plane connection which is applied to the juxtaposed collectors of the electrodes of the same polarity.
According to the document EP-0 029 925, the electric coupling is carried out by means of a full disk arranged then welded on the winding section of the spirally wound electrodes.
For example the document U.S. Pat. No. 4,009,053 describes a generator with alkaline electrolyte and spirally wound electrodes. It shows a plane circular connection carrying radial slots having the form of lances, the turned-down edges of which serve to establish the electric contact with the collector of the spirally wound electrode.
In electrochemical generators with aqueous electrolyte such as the Ni—Cd generators, the electrode support is a nickel-coated steel strip approximately 0.2 mm thick. There are no particular difficulties with welding directly to the strip section a piece electrically connected to the terminal. On the other hand, in electrochemical generators with organic electrolyte with which the invention is concerned, such as lithium generators or supercapacitors, the support of the positive electrode is generally a thin aluminum strip less than 50 μm thick and that of the negative electrode is a thin copper strip less than 50 μm thick. Such thinnesses do not offer the mechanic resistance necessary for producing reliable welds on the electrode section.
From the document EP 1 102 337 an electrochemical generator is known comprising an alternating sequence of spirally wound positive and negative electrodes constituting an electrochemical bundle. Each electrode comprises a metal strip serving as a current collector. The strips of the same polarity respectively jut out towards the outside of the bundle in order to form a plane base on which a plane connection is attached.
The portions of the strips jutting out on either side of the electrochemical bundle do not however form a continuous plane base. The strips are folded at 90° by a pressing tool. Such a method does not make it possible to produce a metal barrier with folded strips forming a continuous plane base.
As regards techniques developed within the context of electrode plates (not spirally wound), the document FR-2 748 606 proposes for example a method of connection by expansion. The edges of the electrodes are put together in two semi-bundles coupled horizontally to the current output terminal.